Print it Yourself

• 1). Design the item you are printing on a computer-aided design program such as AutoCAD and save it as an .stl file. That is the industry standard, although some 3D printers might accept other file formats. To print in 3D your design has to be in 3D.
  
  
• 2). Hook up a 3D printer to your computer and make sure it has enough plastic to make your prototype.
  
  
• 3). Open your design document and hit "Print." Then watch in amazement as your design is rendered in plastic before your eyes. A 3D printer works by adding layers about 20 to 30 microns thick of molten plastic until the object takes shape. Besides plastic, a 3D printer can print in wax or metal. Some 3D printers can even print in chocolate, wood, ceramic or -- on the extreme edge of the technology -- human cells. At the time of publication, doctors have successfully "printed" working human kidneys and bladders for transplant.
  
  

Send It to a Third Party for Printing

• 1). Choose a company to make your plastic prototype for you. Some online options include QuickParts, i.materialise and Shapeways. Any one of these companies can 3D print your design in plastic and send it to you.
  
  
• 2). Send your 3D CAD file in .stl format to the company and pay the fee for the service. Some companies walk you through the process more while others expect you to know what you are doing. Shop around and read the fine print before you commit.
  
  
• 3). Look for confirmation that the file was accepted and approved, and wait for your plastic prototype to arrive in the mail.
  
  

The Low-Tech Way

• 1). Print or sketch your design on paper with all measurements clearly labeled.
  
  
• 2). Cut flat pieces out of sheets of plastic using a craft knife and a ruler according to your design.
  
  
• 3). Cast pieces that are not flat using whatever plastic casting method you want. Resin casting is the easiest method for a small-scale project. For resin casting, first sculpt your piece in clay. Let the clay dry. Cover it with room-temperature vulcanizing silicone to make a mold. Pour resin into the mold and let it cure before removing the piece.
  
  
• 4). Glue the pieces of your prototype together with model glue.